The invention relates to the anchoring of a ring tensioning member in a circular container, especially a concrete tank or a concrete tube, and to an apparatus for accomplishing the same.
Circular containers as, e.g., concrete tanks, concrete pipes, etc. have been successfully prestressed since some time. Thereby there is primarily the task to insert the ring cables in the wall which cables are prestressed in order to produce a tangential pressure in the wall of the container. Due to this arrangement the wall remains without cracks, when the inside pressure, e.g. the fluid pressure or the pressure of a loose material is acting on the same. The additional longitudinally extending cables which are often inserted in the wall in order to produce a prestress force in the direction of the main axis of the container have no importance whatsoever as far as the present invention is concerned and therefore they will not be contemplated in the following description.
The tangential prestress force which is also called the ring prestress force is divided, because of the friction losses, into individual sections of the container circumference so that the individual cables usually span over 90.degree., 120.degree., 180.degree. and only exceptionally over 360.degree. of the circumference of the container.
The known prestressed free standing concrete tanks have one or more anchorage elevations on their external surface; in these elevations the individual cables are anchored.
The known prestressed pressure tunnels which are built in rocks have the same anchorage elevations on the internal wall surface of the tunnel; the individual cables are equally anchored in these anchorage elevations. When in case of a concrete tank e.g. three cables are inserted in the circumference wall of the container, three anchorage elevations have to be made for such a cable on the external surface of the container, whereby every end of the same cable is anchored in the neighboring two anchorage elevations. In case of a pressure tunnel the anchorage of the individual cables is to be carried out in the same way as with the concrete tanks, however with the difference that the anchorage elevations are to be made on the internal wall surface of the tunnel. Owing to the anchorage elevations jutting out inwards the hydraulic flow conditions are deteriorated.
The fact that the cable ends have to be brought out of the wall in order to anchor and prestress the cables brings problems concerning stations of construction and esthetical appearance, and besides considerable economical disadvantages. The object of the invention is to do away with the above mentioned disadvantages and to propose first of all an apparatus for anchoring a ring tensioning member in a circular container which would be simple. The jutting-out anchorage elevations should be generally eliminated in order to achieve a constant wall thickness of the container over its whole circumference and to substantially reduce the number of the ring tensioning member anchorages.